HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Feb 26, 2013, 03:53 AM
dro56595@bigpo's Avatar
Australia, NSW, Williamtown RAAF
Joined Aug 2008
2,466 Posts
My 2c,

whether the hole will suck or blow will be effected by how much dynamic pressure can be generated in the duct/tube/hose via efflux velocity.

High efflux velocity means high dynamic pressure which in turn reduces the static pressure in the duct/hose (bernoulli stuff) which may induce a static pressure differential between each end of the vent tube ...

... especially when there's a ram air effect/stagnation pocket in the ESC pit increasing the relative static pressure in that side of this system.

Whether the power setup in this model is strong enough to produce that effect is the question ...
dro56595@bigpo is online now Find More Posts by dro56595@bigpo
RCG Plus Member
Last edited by dro56595@bigpo; Feb 26, 2013 at 04:14 AM.
Reply With Quote
Sign up now
to remove ads between posts
Old Feb 26, 2013, 03:53 AM
Registered User
Joined Jul 2007
2,086 Posts
OMG....................

Where did you come from?????????

Apparently, the Royal Australian Air Force.................
davemilw07 is offline Find More Posts by davemilw07
Last edited by davemilw07; Feb 26, 2013 at 04:09 AM.
Reply With Quote
Old Feb 26, 2013, 04:13 AM
dro56595@bigpo's Avatar
Australia, NSW, Williamtown RAAF
Joined Aug 2008
2,466 Posts
Quote:
Originally Posted by davemilw07 View Post
OMG....................

Where did you come from?????????

Apparently, the Royal Australian Air Force........
Yeah, been around a while. Don't have all day to get embroiled in these discussions.

But it's always fun to catch up
dro56595@bigpo is online now Find More Posts by dro56595@bigpo
RCG Plus Member
Old Feb 26, 2013, 04:17 AM
Registered User
Joined Jul 2007
2,086 Posts
Quote:
Originally Posted by dro56595@bigpo View Post
Yeah, been around a while. Don't have all day to get embroiled in these discussions.

But it's always fun to catch up
Hey,

Welcome to the club, I hope that you will stick around for a while...........

I always appreciate an expert opinion!!!!!
davemilw07 is offline Find More Posts by davemilw07
Last edited by davemilw07; Feb 26, 2013 at 04:33 AM.
Reply With Quote
Old Feb 26, 2013, 04:39 AM
Registered User
Australia, VIC, Melbourne
Joined Nov 2006
11,508 Posts
7S 1840kv would be almost a dead match for 6S 2200kv. Fractional less power.
1690kv for 8S to near match 6S 2200kv

And for psycho power 'needful' people... it means you could run 8S much higher power totals too. I don't think 2x 4S would not fit (lengthwise). eg 1840kv's

Or 6S 2040's to cut down a bit on the hungry needs of 2200kv.

The motors are approx $63 each. That is half way between Lander/CP and HET.... and their specs and claims are closer to the HET side, possibly the same people making both really.

I have "eight decisions" to currently make about a bunch of aircraft and things..... so I have to balance out what I exactly get for what.
eg a bunch of motors, and the Leopards are a two week pre-order for 'odd' non-common sizes (all those above). Plus I only have two 7S batteries, for another jet, and don't wan't to commit to mroe 7S unless it is worth it - so the Su needs some thought first. But its HETs would have somewhere to go, so that is some help.
Eeeny meeny miny mo....
PeterVRC is online now Find More Posts by PeterVRC
RCG Plus Member
Last edited by PeterVRC; Feb 26, 2013 at 04:49 AM.
Reply With Quote
Old Feb 26, 2013, 05:50 AM
Registered User
genghiskt's Avatar
Joined Sep 2011
262 Posts
Quote:
Originally Posted by PeterVRC View Post
7S 1840kv would be almost a dead match for 6S 2200kv. Fractional less power.
1690kv for 8S to near match 6S 2200kv

And for psycho power 'needful' people... it means you could run 8S much higher power totals too. I don't think 2x 4S would not fit (lengthwise). eg 1840kv's

Or 6S 2040's to cut down a bit on the hungry needs of 2200kv.

The motors are approx $63 each. That is half way between Lander/CP and HET.... and their specs and claims are closer to the HET side, possibly the same people making both really.

I have "eight decisions" to currently make about a bunch of aircraft and things..... so I have to balance out what I exactly get for what.
eg a bunch of motors, and the Leopards are a two week pre-order for 'odd' non-common sizes (all those above). Plus I only have two 7S batteries, for another jet, and don't wan't to commit to mroe 7S unless it is worth it - so the Su needs some thought first. But its HETs would have somewhere to go, so that is some help.
Eeeny meeny miny mo....
Pete,
I can get you the Leopards if you need. But I don't use them. PM me.
genghiskt is offline Find More Posts by genghiskt
Reply With Quote
Old Feb 26, 2013, 05:52 AM
Registered User
Joined Jul 2007
2,086 Posts
Quote:
Originally Posted by dro56595@bigpo View Post
Yeah, been around a while. Don't have all day to get embroiled in these discussions.

But it's always fun to catch up
Just out of curiosity, what sort of full-scale jets have you flown???

You would be a total expert on this type of subject!!!!!

BTW, I would have loved to have been a jet fighter pilot, but my eyesight prevented me from doing that, so I can only imagine.............
davemilw07 is offline Find More Posts by davemilw07
Last edited by davemilw07; Feb 26, 2013 at 06:00 AM.
Reply With Quote
Old Feb 26, 2013, 06:06 AM
Registered User
United States, AR, Jacksonville
Joined Jul 2004
494 Posts
Hey Dave,

Millitary pilots are very specialised and pretty much only know what it takes to operate their airframe. Their systems and technical knowledge of their aircraft is usually sufficient, but the physics and engineering involved is usually nonexistent.
Whiskey Whiskey is offline Find More Posts by Whiskey Whiskey
Reply With Quote
Old Feb 26, 2013, 06:11 AM
Registered User
Joined Jul 2007
2,086 Posts
Yes, but I understand all of it, so it would be a real trip for me..................

Chuck Yeager was my idol, when I was growing up.........
davemilw07 is offline Find More Posts by davemilw07
Last edited by davemilw07; Feb 26, 2013 at 06:36 AM.
Reply With Quote
Old Feb 26, 2013, 07:02 AM
Life begins at transition
Australia, VIC, Sale
Joined May 2007
3,593 Posts
Good to see someone finally mentioned static and dynamic pressure!
Bernoulli and Venturi are two words thrown around when demonstrating the effect. Conservation of mass, momentum and energy are the three theories behind it all.

I'd expect the airflow to be from aft to forward, based on expected static pressure. BUT: Flow vis will sort it out. Wool tufts and cameras are very widely used for in-flight measurements like this.

WW:
Not sure if that's how the USAF work, but I'd be extremely surprised if a pilot couldn't explain the difference between static and dynamic pressure.
Odysis is offline Find More Posts by Odysis
Reply With Quote
Old Feb 26, 2013, 07:21 AM
Scott
Australia, SA, Two Wells
Joined Feb 2012
216 Posts
I'm no sure why there is so much theory going around this motor wire hole debate. Pretty simple test would be to hang a piece of cotton next to the hole and see if its blown away or sucked in. I think it would be blown away cause its too much of a dirty hole to create a vaccum but don't care enough to try it myself.

The best way to cool the esc is not to bother with cutting a bit of extra shrink wrap off or put holes from in front of the ducts to suck through air. I found both of these did little to nothing. Maybe I didn't put big enough holes into the duct from the esc part but there are so many easier cleaner paths for the air to come through (cheaters and duct opening) that it seems to suck very little through when static.

The best thing is to make a small scoop to attach to the esc grill to force air past them as people have mentioned earlier. Simple but so much more affective than any other solution. I have have the exit air going into the duct through the additional hole into the duct but it would have been much easier just to let the air past out through a hole at the back of the servo wire cover.

Just my opinion but I've been there before with other models trying all these little technical thing to do something that could have had a simple solution in the first place. However some do like to tinker so each to their own, I am just time poor due to other commitments unfortunately.
wigsw001 is offline Find More Posts by wigsw001
Reply With Quote
Old Feb 26, 2013, 07:34 AM
Flying Hazard
SU-4ever's Avatar
Spain
Joined May 2006
2,940 Posts
THE WAIT IS OVER.

Su-35 "Svetlana's Rebirth" (14 min 21 sec)


And now comes my long unreadable-hateful post

Quote:
Originally Posted by fredmdbud View Post
Actually, it is quite relevant, because if the fluid was not present, the airflow in the "loop" would allow the pressures would to equalize - no Venturi effect.
No, they wouldn't because when fluid is moving you can idealize a "flow tube" through which the air passes by but doesn't exit through the "walls" of the tube.
That means you can really measure the difference in pressure between both ports ahead and behind the fan but the tube won't be able to equal the pressures. For that you use low cross-section tubes!

The venturi thing you say, you are actually talking about boundary layer detachment. Fluids in motion have a natural tendence to follow curvatures because of its viscosity (An inviscid flow doesn't) and what you are playing with is that at greater speeds the fluid detaches easily because the hole forms like a 90+ angle versus the duct. Its the same principle that governs wing stall. So as long as you leave compressibility effects out of the equation the flow will "ignore" the hole at greater speeds but it still produces drag and turbulence and makes the whole system loose efficiency.
SU-4ever is offline Find More Posts by SU-4ever
Reply With Quote
Old Feb 26, 2013, 08:07 AM
Scott
Australia, SA, Two Wells
Joined Feb 2012
216 Posts
That is an awesome vid. Probably the best quality video I've seen on the SU-35 apart from sales videos. Also great flying mate, well done.

Also I've have to be the first to say it. Pretty rough runway. What landing gear have you got on there. I've replaced mine but I don't think it's up to the task and may break on first landing as I have a fairly rough strip too. It's only the hobbyking DSR A retracts rigged with the stock rear legs.
wigsw001 is offline Find More Posts by wigsw001
Reply With Quote
Old Feb 26, 2013, 08:18 AM
Flying Hazard
SU-4ever's Avatar
Spain
Joined May 2006
2,940 Posts
Glad you like it!

Now the runway is pretty fine, you should see how bad it was before removing the gras...
I have more videos of this beauty, you can find most here and see what the runway conditions were like... http://vimeo.com/channels/edfjets/page:2

I use Freewing's stock main struts... from the Eurofighter

The nose gear stays the same and retracts are Ping-Zheng though using the chip and motor from Freewing units.

Cheers!
Jandro.
SU-4ever is offline Find More Posts by SU-4ever
Reply With Quote
Old Feb 26, 2013, 09:43 AM
Registered User
United States, FL, Hollywood
Joined Aug 2010
1,535 Posts
Great video SU-4ever. Good to see you back in the air making videos. Almost makes me want to buy one again.
Wonder if I have enough ceiling room...
urrl is offline Find More Posts by urrl
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion LX F-35 Vs Freewing F-35 Mmarshall Foamy EDFs 17 Jul 09, 2014 07:49 AM
Found SU-34 Freewing lw777pilot Aircraft - Electric - Jets (FS/W) 1 Dec 15, 2013 02:25 PM
New Product Brand New SU-35! 70x2,TV and made by Freewing!Update:Worldwide Availability neversommer Foamy EDFs 593 Jan 09, 2012 10:02 PM
For Sale Freewing SU-34 stock battery - Brand New JGuilty13 Aircraft - Electric - Batteries & Chargers (FS/W) 0 Nov 29, 2011 03:01 PM
For Sale Freewing SU-34 stock battery JGuilty13 Aircraft - Electric - Jets (FS/W) 0 Nov 29, 2011 11:29 AM